Apparatus for damping pulses in a fluid



- April 28, 1964 K. LOPAS 3,

APPARATUS FOR DAMPING PULSES IN A FLUID Filed May 16, 1962 5 Sheets-Sheet 1 INVENTOR It KASIMIR LOPAS g 4 MW April 28, 1964 K. LOPAS APPARATUS FOR DAMPING PULSES IN A FLUID 5 Sheets-Sheet 2 Filed May 16, 1962 INVENTOR. I KASIMIR LOPAS BY W YK P SW his ATTORNEYS April 28, 1964 K. LOPAS 3,130,751

APPARATUS FOR DAMPING PULSES IN A FLUID Filed May 16, 1962 5 Sheets-Sheet 3 F/GI 6 "(4 6 68 -...J l00 H 13 H IOI. INVENTOR KASIMIR LOPAS ,3

76 EM QMXQW 73 his ATTORNEYS April 28, 1964 Filed May 16, 1962 K. LOPAS APPARATUS FOR DAMPING PULSES IN A FLUID 5 Sheets-Sheet 4 his INVENTOR. KASIMIR LOPAS ATTORNEYS April 28, 1964 K. LOPAS 3,130,751

APPARATUS FOR DAMPING PULSES IN A FLUID Filed May 16, 1962 5 Sheets-Sheet 5 INVENTOR. KASI MIR LOPAS ATTORNEYS United States Patent 3,130,751 APPARATUS FOR DAR/ PING PULSES IN A FLUID Kasimir Lopes, Stamford, Comm, assignor to Time, In-

corporated, New York, N.Y., a corporation of New York Filed May 16, 1%2, Ser. No. 195,290 16 Claims. (Cl. 138-30) This invention relates to apparatus for damping pulses in a fluid and, more particularly, to novel and highly effective apparatus for damping pulses in a liquid such as paper stock.

In the manufacture of paper from a paper stock by the discharge of the stock through a slice and onto a Fourdrinier wire, the stock should be as nearly free of pulses as possible when it is delivered to the slice, so that small random samples of the resulting paper web formed on the wire will be of substantially identical character.

Conventional pulse-damping apparatus typically is relatively massive and formed with numerous orifices, obstructions and dead spaces. As a result, it achieves insuflicient coupling with the pulses in the fluid and fails effectively to damp them. Further, the orifices, obstructions and dead spaces promote hang-up of stock, so that the apparatus for damping the pulses may be not only useless but detrimental to the paper-making process.

An object of the present invention is to provide novel and highly-effective pulse-damping apparatus which overcomes the above-noted and other disadvantages of conventional apparatus.

In particular, an object of the invention is to provide pulse-damping apparatus which achieves maximum coupling with the pulses to be damped and which is formed with no orifices, obstructions or dead spaces.

Another object of the invention is to provide pulsedamping apparatus which is adapted to damp pulses in a fluid of which the instantaneous mean pressure in the vicinity of the apparatus may vary over a wide range.

These and other objects are accomplished by providing, in a first representative embodiment of the invention, a flexible diaphragm in contact on one side with a fluida paper stock, for example-in which there are pulses to be damped and on the other with the interior of an air-filled chamber. An air-supply line is provided for supplying air under pressure to the chamber, and an air-exhaust line is provided for exhausting the air from the chamber. A valve connected to the air-supply line and the airexhaust line controls their conductances, and a valveactuating member connected to the diaphragm and the valve controls the valve. The arrangement is such that an incipient stretching of the diaphragm due to a change in the instantaneous mean pressure of the fluid in the vicinity of the diaphragm produces a corresponding change in the instantaneous mean pressure of the air in the chamber, so that the diaphragm is not stretched but rather is maintained in condition to vibrate in response to the pulses and damp them.

An understanding of further particulars of the invention may be gained from the following detailed description of several representative embodiments thereof and from the accompanying figures in the drawings, of which:

FIGURE 1 is a bottom plan view, partly in section, of a first representative embodiment of apparatus constructed in accordance with the invention for damping pulses in a fluid;

FIGURE 2 is a view taken substantially along the line 22 in FIGURE 1, but rotated 90 clockwise, and looking in the direction of the arrows;

FIGURE 3 is an enlarged view taken substantially along the line 33 in FIGURE 2 and looking in the direction of the arrows;

3,130,751 Patented Apr. 28, 1964 FIGURES 4 and 5 are alternate embodiments of a portion of the apparatus shown in FIGURES 1 and 2;

FIGURE 6 is an elevational view, partly in section, of a fourth embodiment of apparatus constructed in accordance with the invention for damping pulses in a fluid;

FIGURE 7 is an elevational view, partly in section, of a fifth embodiment of apparatus constructed in accordance with the invention for damping pulses in a fluid;

FIGURE 8 is a view taken substantially along the line 8-8 in FIGURE 7 and looking in the direction of the arrows; and

FIGURE 9 is an enlarged view taken substantially along the line 99 of FIGURE 8 and looking in the direction of the arrows.

In the following detailed description and in the accompanying drawings, corresponding parts of the first, second, third, fourth and fifth embodiments are designated by like reference characters respectively without superscript and with the superscripts 1, 2, 3 and 4.

FIGURES 1 and 2 show a pipe 10 adapted to contain a fluid such as a paper stock 11. The pipe 10 comprises pipe sections ltla, 10b and lilc which are joined sealably together in end-to-end fluid-conducting relation. In order to facilitate union of the pipe sections, the middle section 10b is formed at its opposite ends 12 and 13 with outwardly-extending circular flanges 14 and 15 having holes 16 and 17 adapted to receive eXteriorly-threaded bolts 18 and 19, respectively. Likewise, the pipe sections 10a and adjacent to the section 10b at opposite ends thereof are formed at their ends 22 and 23 with outwardly-extending circular flanges 24 and 25 having holes 26 and 27, respectively, which correspond in shape, size and position to the holes 16 and 17. Nuts 28 and 29 having interior threads complemental to the exterior threads of the bolts 18 and 19 co-operate with the bolts 18 and 19, respectively, to draw the flanges 14 and 24 on the one hand and 15 and 25 on the other tightly against sealing means such as annular gaskets 30 and 31 positioned between the flanges 14, 24 and the flanges 15, 25, respectively. Holes 32 and 33 formed in the gaskets 3i) and 31 are complemental to the holes 16, 26 and 17, 27 and receive the bolts 18 and 19, respectively. A fluid-tight seal is thus formed between the pipe sections 19a, 10b and 100, and additional sections may be hooked up in the same manner to form the pipe 10.

In any fluid transported in a pipe such as the pipe 10, there are likely to be pulses unavoidably generated in a number of ways. For example, a pump used to drive the fluid is typically inherently also a pulse generator. In applications such as paper making, it is desirable that the pulses be damped. To this end, there is provided in accordance with the invention apparatus indicated generally by the reference numeral 34 for damping pulses in a fluid. The apparatus 34 comprises a flexible member such as a diaphragm 35 which may be circular and made of nylon-reinforced rubber and formed with circular corrugations 36 concentric with the diaphragm 35.

The diaphragm 35 is in contact on one side with the stock 11 or other fluid in the pipe 10 and on the other with the interior 37 of a hollow, Walled, airtight chamber 33 which contains a fluid such as air adapted to permit vibratory movement of the diaphragm 35 in response to pulses in the stock 11. As FIGURES 1 and 2 show, a portion of the diaphragm 35 forms a portion of a wall of the chamber 38.

The pipe 10 is slightly enlarged in the vicinity of the diaphragm 35 by a short, hollow, generally cylindrical protuberance 39 joined to and communicating with the pipe 10. The line 39a (only the far half of which is visible in FIGURE 2, the near half being cut away) of intersection between the pipe 10 and the protuberance 39 has the shape of a projection of a circle of given radius in a direction normal to the plane of the circle on a cylinder of the same radius, the line normal to the circle and passing through its center being normal to the axis of the cylinder. The lower end of the protuberance 39 is joined to a frustum-shaped member 40 along a circular path 40a. The diameter of the circular path 40a which is perpendicular to the plane of FIGURE 2 is substantially collinear with a generatrix of the cylinder formed by the pipe 10.

Inasmuch as the path 40a does not extend into the cylindrical portion of the pipe 10, there is no obstruction to the flow of stock 11 within that portion. Further, the frusturn-shaped member 49 does not greatly enlarge the pipe and provides a smooth flow path for the stock 11 as it passes the diaphragm 35, so that no dead spacesi.e., areas in which fluid flow stops or substantially decreasesar e created. Moreover, no orifices or other structures forming small or tortuous paths for the flow of stock 11 are necessary to the operation of the apparatus 34. Finally, the structure is such that a minimum of mass must be moved by the pulses, so that the pulses are not reflected but are absorbed with great efficiency.

To facilitate proper mounting of the diaphragm 35, a front plate 41 is formed with an aperture having frust'um-shaped Walls 42 complemental to the member 40 for rigid connection to the member 40. A ring 43 is provided with holes 44 and the plate 41 with holes 45 interiorly threaded to receive bolts 46, whereby the diaphragm 35 may be held securely between the plate 41 and the ring 43 along the circumference of the diaphragm 35. For reasons which will be set forth hereinafter, it is preferred that the diaphragm 35 be mounted horizontally and below the pipe 10 as shown.

Rigid members 47 connected to the ring 43 form a supporting lattice generally concave towards the diaphragm 35 and may prevent its rupture or stretching beyond its elastic limit in the event of a breakdown of the means hereinafter described for maintaining the instantaneous mean pressure in the interior 37 of the chamber 38 equal to the instantaneous mean pressure of the stock 11 in the vicinity of the diaphragm 35. The rigid members 47 also perform a mounting function, as hereinafter described.

The interior 37 of the chamber 38 is variable in volume, so that pulses of different amplitude may be damped with maximum efliciency. If the expected pulses are of low amplitude, the volume of the interior 37 may be relatively small; if of greater amplitude, the volume of the interior 37 may be enlarged.

In accordance with a preferred means for varying the volume of the interior 37, the chamber 38 is constructed in three sections: the diaphragm 35 and front plate 41 already referred to, a cylindrical portion 49, and an end plate 50. Annular sealing means such as gaskets 51 and 52 seal the cylindrical portion 49 to the front plate 41 and to the end plate 50, respectively. Long bolts 53 are passed through apertures 54 in the end plate 50 and screwed into threaded apertures 55 in the plate 41 in order to hold the chamber 38 together. To substitute a chamber having a size different from that of the chamber 38, it is necessary merely to remove the bolts 53 and the cylindrical portion 49 and replace them with other bolts and another cylindrical portion having lengths different from those of the bolts 53 and the cylindrical portion 49.

The instantaneous mean pressure of the stock 11 or other fluid in the vicinity of the diaphragm 35 is of course a function of a number of variables including its velocity in the pipe 10. In many cases it is desirable to vary the velocity of the stock 11 within a considerable range. The resulting variation of the instantaneous mean pressure of the stock 11 in the vicinity of the diaphragm 35 produces in incipient stretching of the diaphragm 35 either upwardly or downwardly, depending 4 on whether the pressure of the stock 11 decreases or increases. Such movement, if not counteracted, would ultimately stretch the diaphragm 35 to the point where it was no longer in condition to vibrate or flex in response to the pulses in the stock 11, in which case the apparatus 34 would not effect damping of pulses.

In accordance with the invention, therefore, means are provided for producing changes in the instantaneous mean pressure of the air in the chamber 38 equal to the changes in the instantaneous mean pressure of the stock 11 or other fluid in the vicinity of the diaphragm 35, whereby the diaphragm 35 is not stretched by changes in the instantaneous mean pressure of the stock but is maintained in condition to vibrate in response to the pulses and damp them.

In the embodiment of FIGURES 1 and 2, a gasor other fluid-supply means such as an air-supply line 56 is provided for supplying air to the interior 37 of the chamber 38, and a gasor other fluid-exhaust means such as an air-exhaust line 57 is provided for exhausting air or permitting its escape from the interior 37 of the chamber 38. The air-supply line 56 extends through an aperture 53 in the front plate 41 and communicates with conventional apparatus such as a tank of compressed air or an air pump (not shown). The air-exhaust line 57 passes through an aperture 59 in the front plate 41 and discharges to a sink, normally the atmosphere. Obviously, the line 57 may discharge instead into a relative vacuum or even into a sink having greater-than-atmospheric pressure.

The conductances of the air-supply line 56 and the airexhaust line 57 are controlled by a valve 60 mounted on the rigid members 47 by bolts 61 and having a valve member 62 slidably positioned in a bore 63. The valve member 62 is urged by biasing means such as an expansion coil spring 64 against a cam surface 65 formed on a rigid valve-actuating member 66 attached to the diaphragm 35. A block 67 provided with a bore 68 in which the valve-actuating member 66 is slidable guides the member 66 so that it moves in a line normal to the plane of the diaphragm 35. Bolts 6% passed through apertures 70 formed in lugs 71 attached to the block 67 and into interiorly-threaded apertures 72 in the members 47 secure the block 67 to the members 47. The valve 60 has a common port 73 through which air may enter the interior 37 of the chamber 38 from the air-supply line 56 or leave the interior 37 of the chamber 33 through the air-exhaust line 57, depending on the position of the valve member 62.

As FIGURE 3 shows, the end portions 74 and 75 of the valve member 62 normally substantially seal the bore 63 in the vicinity of the airsupply line 56 and the airexhaust line 57, respectively. The center portion 76 of the valve member 62 is of reduce diameter and, if in communication with the air-supply line 56 or the airexhaust line 57, permits passage of air through the port 73 and respectively into or out of the interior 37 of the chamber 38.

The sliding of the valve member 62 within the bore 63 in the directions of the double-headed arrow is etfected by movement of the diaphragm 35, the valve-actuating member 66 and the cam surface 65. The cam surface 65 has a central operating portion 65a (FIGURE 2) which is preferably inclined at a small angle, less than 7, for example, with respect to the direction of movement of the valve-actuating member 66. The best results in tests of apparatus constructed in accordance with the invention have been achieved with an angle of about 3 /2. The end of the valve member 62 in contact with the cam surface 65a may be conical, forming an angle supplemental to twice the angle of the surface 65a with respect to the direction of movement of the valve-actuating member 66. End portions 65b and 650 of the cam surface 65 form a greater angle than 7 with respect to the direction of movement of the valve-actuating member 66.

The slopes of the portions 65a, 65b and 650 with respect to the direction of movement of the valve-actuating member 66 have like sign.

Workmen skilled in the art will understand from the preceding disclosure that, as the instantaneous mean pressure of the stock ll in the vicinity of the diaphragm 35 increases, initiating a downward stretching of the diaphragm 35 as seen in FIGURE 2, the slope of the cam surface 65 allows the coil spring 64 to expand and force the valve member 62 to the left as seen in FIGURE 2, moving the reduced portion 76 of the valve member 62 (FIGURE 3) into communication with the air-supply line 56 and the port 73, so that air is delivered under pressure through the air-supply line 56 and the port 73 to the interior 37 of the chamber 38, thereby raising the pressure of the air in the chamber 33. The increased pressure in the chamber 38 almost instantly moves the diaphragm 35, the valve-actuating member 66 and the cam surface 65 upwardly, thereby forcing the valve mem ber 62 to the right as seen in FIGURE 2 and compressing the spring 64. The diaphragm 35 is therefore soon restored to its neutral position, and the portion 74 of the valve member 62 thereupon seals oil the air-supply line 56 from the port 73, so that substantially no further air is admitted to the interior 37 of the chamber 38.

If the instantaneous mean pressure of the stock 11 in the vicinity of the diaphragm 35 drops, the pressure of the air in the interior 37 of the chamber 38 initiates a stretching of the diaphragm 35 and a movement of the valve-actuating member 66 and the cam surface 65 upwardly as seen in FIGURE 2, thereby forcing the valve member 62 to the right as seen in FIGURE 2 and further compressing the spring 64. This movement of the valve member 62 immediately brings the reduced portion 76 of the valve member 62 into communication with the air-exhaust line 57, thereby allowing air to escape from the interior 37 of the chamber 38 through the port 73 and the air-exhaust line 57. When the pressure in the interior 37 of the chamber 38 drops sufficiently owing to the loss of air, the pressure of the stock 11 forces the diaphragrn 35, the valve-actuating means as and the cam surface 65 downwardly as seen in FIGURE 2 so that the spring 64 moves the valve member 62 to the left as seen in FIGURE 2, allowing the portion 75 to seal the airexhaust line 57 so that substantially no further air escapes from the interior 37 of the chamber Regardless of changes in the instantaneous mean pressure of the stock ll in the vicinity of the diaphragm 35, therefore, the instantaneous mean pressure of the air in the interior 37 of the chamber 38 is substantially equal to the pressure of the stock, so that the diaphragm 35 is stretched neither upwardly nor downwardly but remains in condition to vibrate in response to pulses in the stock and damp them.

FIGURE 4 shows a different type of flexible member, namely a bellows 843 having at one end thereof a radially-flaring portion 81 which may be compressed by \bolts 46 between a front plate 41 and a ring 43 A valve-actuating member 66 is attached to the bellows: 80 and controls the movement of a cam surface corresponding to the cam sunface 65. The function of the bellows 3% is therefore analogous mo that of the diaphnagm 35 in the embodiment of FIGURES 1 and 2.

The bellows 80 may have a generally cylindrical shape and be formed with circular corrugations -82 which permi t an oscillatory lengthening and shortening of the bellows 8d response to pulses in the stock 11 whereby the pulses are damped. corrugations 82 formed on the bellows 8-1} may be substantially coaxial with the bellows as shown.

FIGURE shows a bellows 83 having generally the shape of a short tube of which a portion 84 is rolled back upon itself. This construction likewise permits os- 6 oillatory movement oi a valve-actuating member 66 in such a way as to damp pulses in the stock 11 The bellows of FIGURES 4 and 5 are of course adapted not only to damp pulses but also to be combined with means (not shown in FIGURES 4 and 5) such as the means of FIGURES l and 2 for producing changes in the instantaneous mean pressure of the air in the chamber 38 equal to the changes in the instantaneous mean pressure of the stock or other fluid in the vicinity of the bellows.

In paper-making applications, the diaphragm 35 is preferred to the bellows Si) and 83 because a paper stock moves more freely in the vicinity of the diaphragm 35 sh m the vicinity of the bellows 8t) and 83 and hence is less likely to hang up. The bellows and 33 may be used, however, in cases where the amplitude of the pulses in lthe stock is very great, inasmuch as a valveactuating member is adapted for greater movement when it is attached to a bellows such as the bellows 80 or $3 than when it is attached to a diaphragm such as the diaphnagm 35.

FIGURE 6 shows a more sophisticated embodiment of apparatus constructed in accordance with the invention for damping pulses in a fluid. A pulse-damping app aratus 34 is attached to a pipe 10 containing a stock 11 The apparatus 34 is substantially the same as and may in fact be identical to the apparatus of FIG- URES 1-3, except that the apparatus 34 further comprises differential-pressure-regulator means designated genenally by the numeral '83. The differential-pressure regulator 88 is mounted a gasor other fluid-supply means such as an air-supply line 56 which extends into a chamber 38 and to a valve 60 which may be similar or identical to the chamber 38 and valve 60, respectively. A gasor other fluid-exhaust means such as an air-exhaust line 57 extends from the valve 69 to a sink such as the atmosphere.

A feedback line 89 communicate-s at one end with the interior 37 of the chamber 38 and at the other with the interior 9% of a hollow, walled, air-tight chamber 91 in che diiferential-pressure regulator 8-8. Obviotusly, the pressure of the air within the interior 90 of the chamber 91 is the same as the pressure of the air within the interior 37 of the chamber 38 The differential-pressure regulator 8-8 is provided with a valve member 92 slidable in the air-supply line 56 and of somewhat smaller diameter than the bore 93 of the air-supply line 56 and adapted in cooperation with a valve seat 94 selectively to block or permit flow of air under pressure in the direction indicated by the arrow. The ditferential-pressure regulator 88 in combination with the valve 60 therefore controls the conductance of the air-supply line 56 Movement of the valve member 92 within the bore 93 is controlled by movement of a flexible member such as a diaphragm 95 at least a portion of which forms at least a portion of a Wall of the chamber 91. A biasing means such as a compression coil spring '96 having an end '97 positioned by a control knob 98 threadably inserted in airtight relation through an opening 99 in the chamber 91 biases the valve member 92 towards the open position with respect to the valve seat 94. The downward force exerted by the spring 96 on the diaphragm 9.5 may be such that the valve member 92 is in the open position unless the pressure in the air-supply line 56 is, say, .10 pounds per square inch greater than the pressure in the chamber 91.

If the control knob 98 is initially so set, the differenrial-pressure regulator '88 maintains this differential pressure regardless of changes of the mean pressure of the stock 11 and hence regardless of changes of pressure in the interior 37 of the chamber 38 For example, if the mean pressure of the stock 11 increases, forcing the diaphragm 35 the valve-actuating member 66 and the camv surface 65 downwardly, whereby air is admitted from the air-supply line 56 to the interior 37 of the chamber 33 the increased pressure in the interior 3'7 of the chamber 33 which is transmitted to the interior 90 of the chamber 91, and the momentarily decreased. pressure in the portion. of the air-supply line 56 between the differential-pressure regulator 88 and the valve 63 permit the spring 95 to force the diaphragm 95 downwardly and unseat the valve member 92 from the valve seat 94. More .air thereupon admitted into the portion of the lair-supply line 56 between the differentialpressure regulator 88 and the valve: 69 whereby the pressure of the air in that portion of the air-supply line 56 increased by an amount equal to the increase of the pressure of the gas in the interior 37 of the chamber 33 When the pressure in the air-supply line 56 once again exceeds that in the interior 37 of the chamber 38 land the interior 9% of the chamber 91 by pounds per square inch, the spring 96 is unable to keep the valve member 92 in the open position, and it closes.

Similarly, if the pressure of the stock 11 drops, so that the pressure of the air in the interior 37 of the chamber 38 initiates an upward stretching of the diaphragm 35 and an upward movement of the valve-actuating member 66 and the cam surface 65 allowing air to escape from the interior 3-7 of the chamber 38 through the airexhaust line 57 the decreased pressure of the air in the interior 37 of the chamber 38 produces an equal decrease of the pressure of the air in the interior 9t? of the chamber 9-1. The valve member 92 is therefore held tightly in its valve seat 94. While this does not produce an instantaneous decrease in the pressure of the air in the portion of the air-supply line 56 between the differential-pressure regnilator S8 and the valve 69 leakage of air by the valve 60 quickly (within about half a second, in one embodiment of apparatus constructed in accordance with the invention) reduces the pressure of the air in the portion of the air-supply line 56 between the differential-pressure regulator 88 and the valve 60 until that pressure is 10 pounds per square inch greater than the pressure of the air in the interior 9d of the chamber 91. Further decrease in the pressure of the air in the portion of the air-supply line 56 between the differential-pressure regulator 88 and the valve 611 is prevented by downward movement from time to time as necessary of the valve member 92 as hereinbefore explained.

Thus, the differential pressure between the air in the air-supply line 56 adjacent to the valve M9 and the air in the interior 37 of the chamber 38 is maintained at a desired value regardless of fluctuations in the mean pressure of the stock 11 over a wide range.

Gauges G and G in the supply line 56 and feedback line 89 indicate the pressures in those lines, respectively.

The differential pres-sure between the air in the airsupply line 56 and the air in the chamber 38 should generally be in the neighborhood of 10 pounds per square inch in paper-making applications. The differential pressure between the air in the chamber 38 and the air in the sink to which the air-exhaust line 57 discharges is of course dependent on the pressure of the air in the chamber 38 During the manufacture of paper, the stock 11 and hence the air in the chamber 38 are typically under a variable pressure which at a given time may be, for example, 25 pounds per square inch gauge.

In order to make the response characteristics of the apparatus 34 the same when it is compensating for an increasing instantaneous mean pressure of the stock 11 as when it is compensating for a decreasing instantaneous mean pressure of the stock 11 the valve member 62 is so formed that the rates of variation of the conductances of the air-supply line 56 and the air-exhaust line 57 for a given movement of the valve member 62 are substantially inversely proportionate to the differential pressure between the air in the air-supply line 56 and the air in the chamber 38 and the differential pressure between the air in the chamber 38 and the air in the airexhaust line 57 respectively.

The valve member 62 may be identical to the valve member 62 illustrated in detail in FIGURE 3. As FIG- URE 3 shows, the valve member 62 is formed with generally V-shaped notches 1% in the portion 74 and adjacent to the portion 76 and similar notches 101 in the portion 75 and adjacent to the portion 76. The walls of the notches 1% may form dihedral angles larger than those formed by the walls of the notches 10-1; or, if the notches 1th) and 101 are identical in shape, the number of the notches 1% may exceed the number of the notches 101.

As a result, a given movement of the valve member 62 to the left as seen in FIGURE 6 creates a greater opening for the passage of air than does an equal move ment of the valve member to the right from a neutral position, and the greater differential pressure between the chamber 38 and the atmosphere is compensated for by the slower rate at which communication between the two is established. By suitable construction of the valve member 62 with due regard for the differential pressures to be encountered, the response characteristics of the apparatus 34 can be made substantially the same regardless of whether the pressure of the stock 11 is increasing or decreasing and despite the difference between the differential pressure between the air in the lair-supply 'line 56 and the air in the chamber 38 and the differential pressure between the air in the chamber 38 and the air in the air-exhaust line 57 FIGURES 7 and 8 shown an application of apparatus constructed in accordance with the invention in which a flexible member such as a diaphragm 35 is mounted vertically in an elbow m4 of a section of pipe m Such a mounting is, however, generally less advantageous than the mountings previously shown, inasmuch as the diaphragm 35 is exposed to greater hydrostatic pressure in the mea Hi5 below a rigid valve-actuating member 66 than in the area .106 above the member 66 The difference in hydrostatic pressure produces a bowing of the diaphragm 35 to the right as seen in FIGURE 7 in the area 1G5 and to the left in the area 166 when the valve- .actuating member 66 is in its neutral position. The diaphragm 35 is thus partially stretched or under tension at all times and is less able to respond to pulses in the stock 11 than are the flexible members previously described. The arrangement of FIGURE 7 may be used, however, when the structure of the paper-making or other apparatus containing a fluid in which there are pulses to be damped is such that a vertical mounting of the diaphragm 35 is more easily effected than a horizontal mounting.

FIGURE 9 shows means for securing a cam surface 65 to the valve-actuating member 66 The valve-actuating member 66 comprises a shaft 167 and a cam unit 108 rigidly held together by set screws 109 passing through apertures lit in the shaft 107 and threadably inserted in interiorly threaded holes 111 in the cam unit 1%. When the set screws 109 are tightened fully, the cam surface 65 is automatically inclined at the desired angle with respect to the direction of movement of the shaft 107 in response to changes in the instantaneous mean pressure of the fluid 11 FIGURE 9 also shows means for securing the valveactuating member 66 to a flexible member such as a diaphragm 35 A flange 112 rigidly connected or or formed on the shaft .107 at the end thereof adjacent to the diaphragm 35 may be bonded to the diaphragm 35 by a suitable adhesive. In addition, a screw 113 passed through an aperture did in the diaphragm 35 and thrcadably received in a hole 115 in the shaft 107 may be employed to provide a strong connection between the diaphragm 35 and the shaft 107. In order to discourage hang-up in paper-making applications, a layer 116 of 9 polytetrafluoroethylene (sold by the E. I. du Pont de Nemours & 'Co. under the trade name Teflon) about .002 inch thick may cover the portions of the diaphragm 35 and the screw 113 which would otherwise be exposed to the stock 11 In order to impart maximum sensitivity to the pulsedamping apparatus of the invention, the moving parts such as the valve member 62 and the valve-actuating member 66 may be made of a light-weight material such as a thermoplastic resin. A material suitable for this purpose is sold by the E. I. du Pont de Nemours & Co. under the trade name Delrin.

Mention has already been made of the fact that it is preferred that the flexible members such as the diaphragm 35 be exposed to substantially equal hydrostatic pres sure over their entire surfaces in contact with the fluid such as the stock 11. It is further desirable, particularly in applications such as paper making that the stock 11 or other fluid be above the diaphragm 35 or other flexible member. Such a construction prevents the accumulation of air bubbles between the stock 11 and the diaphragm 35. The presence of such air bubbles is disadvantageous because it tends to produce hang-up and because the bubbles tend to escape in relatively large sizes with a result that the web of paper formed from the portion of the stock containing the large bubbles is not uniform. A further reason for placing the diaphragm 3'5 or other flexible member under the stock 111 or other fluid is that wave motion in the stock 11 does. not then present a problem. If the diaphragm 35 is above the stock 11, any waves present in the stock 11 may generate spurious movements of the diaphragm 35".

Thus, there is provided in accordance with the invention novel and highly effective pulse-damping apparatus which achieves maximum coupling with the pulses to be damped and which employs no orifices, obstructions or dead spaces. The apparatus of the invention is adapted to provide damping of pulses in a fluid over a wide range of instantaneous mean fluid pressure.

Many modifications of the above-described apparatus within the spirit and scope of the invention will be obvious to workmen skilled in the art. For example, while the means for varying the size of the chamber 38 (FIGURES l and 2) or corresponding chamber in one of the other figures has been described as comprising cylindrical portions substitutive for the cylindrical portion 49 (FIGURES l and 2) or corresponding portion in one of the other figures and having the same diameters but different heights, the substitutive portions may have different diameters as well. Again, a plurality of chambers may be permanently mounted and provided with adjustable openings connecting them so that the volume of gas available for compression and rarefaction in response to movement of the diaphragm 35 or other flexible memher is variable. Further, the air-supply lines such as the line 56 and the air-exhaust lines such as the line 57 may be interchanged and the slope of the cam surfaces such as the surface 65 reversed. Also, the notches 109 and 101 need not be V-shaped but may be U- or otherwise shaped.

Accordingly, the invention is to be construed as including all of the modifications thereof which fall within the scope of the appended claims.

I claim: '1. Apparatus for damping pulses in .a fluid, comprising a flexible member having at least two sides and adapted to be mounted with one of said sides in contact with a first fluid in which there are pulses to be damped,

a hollow, walled chamber connected to said flexible member, at least a portion of said flexible member forming at least a portion of a wall of said chamber, the second side of said member being exposed to the interior of said chamber,

fluid-supply means connected to said chamber for 10 supplying a second fluid to the interior of said chamber,

fluid-exhaust means connected to said chamber for exhausting said second fluid from the interior of said chamber,

valve means connected to said fluid-supply means and said fluid-exhaust means for controlling the conductances of said fluid-supply means and said fluidexhaust means, and

valve-actuating means operatively coupled with said flexible member and said valve means for controlling said valve means, whereby incipient movement of said flexible member in response to a change in the instantaneous mean pressure of said first fluid in the vicinity of said flexible member produces a corresponding change in the instantaneous mean pressure of said second fluid in said chamber for maintaining said flexible member in condition to vibrate in response to said pulses.

2. Apparatus as defined in claim 1 in which the volume of the interior of said chamber is variable.

3. Apparatus for damping pulses in a liquid, comprising a flexible member having at least two sides and adapted to be mounted with one of said sides in contact with a liquid in which there are pulses to be damped,

a hollow, walled chamber connected to said flexible member, at least a portion of said flexible member forming at least a portion of a wall of said chamber, the second side of said member being exposed to the interior of said chamber,

gas-supply means connected to said chamber for supplying a gas to the interior of said chamber,

gas-exhaust means connected to said chamber for exhausting said gas from the interior of said chamber,

valve means connected to said gas-supply means and said gas-exhaust means for controlling the conductances of said gas-supply means and said gas-exhaust means, and

valve-actuating means operatively coupled with said flexible member and said valve means for controlling said valve means, whereby incipient movement of said flexible member in response to a change in the instantaneous mean pressure of said liquid in the vicinity of said flexible member produces a corresponding change in the instantaneous mean pressure of said gas in said chamber for maintaining said flexible member in condition to vibrate in response to said pulses.

4. Apparatus as defined in claim 3 in which said one of said sides is substantially below said liquid.

5. Apparatus for damping pulses in a liquid, comprising a flexible diaphragm having at least two sides and adapted to be mounted with one of said sides in contact with a liquid in which there are pulses to be damped,

a hollow, walled chamber connected to said diaphragm, at least a portion of said diaphragm forming at least a portion of a wall of said chamber, the second side of said diaphragm being exposed to the interior of said chamber,

gas-supply means connected to said chamber for supplying a gas to the interior of said chamber,

gas-exhaust means connected to said chamber for exhausting said gas from the interior of said chamber,

valve means connected to said gas-supply means and said gas-exhaust means for controlling the conductances of said gas-supply means and said gas-exhaust means, and

valve-actuating means operatively coupled with said diaphragm and said valve means for controlling said valve means, whereby incipient stretching of said diaphragm in response to a change in the instantaneous mean pressure of said liquid in the vicinity of 11 said diaphragm produces a corresponding change in the instantaneous mean pressure of the gas in said chamber for maintaining said diaphragm in condition to vibrate in response to said pulses.

6. Apparatus as defined in claim in which said diaphragm is substantially in a horizontal plane and said one of said sides is substantially below said liquid.

7. Apparatus as defined in claim 5 in which said diaphragm is substantially circular and formed with corrugations, said corrugations being substantially concentric with said diaphragm.

8. Apparatus for damping pulses in a liquid, comprising a flexible bellows having at least two sides and adapted to be mounted with one of said sides in contact with a liquid in which there are pulses to be damped,

a hollow, walled chamber connected to said bellows, at least a portion of said bellows forming at least a portion of a wall of said chamber, the second side of said bellows being exposed to the interior of said chamber,

gas-supply means monnected to said chamber for supplying a gas to the interior of said chamber,

gas-exhaust means connected to said chamber for exhausting said gas from the interior of said chamber,

valve means connected to said gas-supply means and said gas-exhaust means for controlling the conductances of said gas-supply means and said gas-exhaust means, and

valve-actuating means operatively coupled with said bellows and said valve means for controlling said valve means, whereby movement of said bellows in response to a change in the instantaneous mean pressure or" said liquid in the vicinity of said bellows produces a corresponding change in the instantaneous mean pressure of the gas in said chamber for maintaining said bellows in condition to respond to said pulses.

9. Apparatus as defined in claim 8 in which said bellows is substantially cylindrical and formed with corrugations, said corrugations being substantially coaxial with said bellows.

10. Apparatus as defined in claim 8 in which said bellows is in the form of a tube having a portion rolled back upon itself.

11. Apparatus for damping pulses in a liquid, comprising a flexible member having at least two sides and adapted to be mounted with on of said sides in contact with a liquid in which there are pulses to be damped,

a hollow, walled chamber connected to said flexible member, at least a portion of said flexible member forming at least a portion of a wall of said chamber, the second side of said member being exposed to the interior of said chamber,

gas-supply means connected to said chamber for supplying a gas to the interior of said chamber,

gas-exhaust means connected to said chamber for exhausting said gas from the interior of said chamber,

valve means connected to said gas-supply means and said gas-exhaust means,

a valve member slidably mounted within said valve means for controlling the conductances of said gassupply means and said gas-exhaust means,

a valve-actuating member operatively coupled with said flexible member, said valve-actuating member being movable in a given direction substantially in a straight line in response to movement of said flexible member and having a cam surface formed thereon at least a portion of which is inclined at an angle of less than 7 with respect to said direction, and

biasing means for urging said valve member against said cam surface, whereby movement of said flexible member in response to a change in the instantaneous mean pressure of said liquid in the vicinity of said member produces a corresponding change in the instantaneous mean pressure of said gas in said chamber for maintaining said flexible member in condition to vibrate in response to said pulses.

12. Apparatus as defined in claim 11 in which at least a portion of said cam surface is inclined at an angle of substantially 3 /2 with respect to said direction.

13. Apparatus as defined in claim 11 in which said portion of said cam surface which is inclined at an angle of less than 7 with respect to said direction is bordered at opposite ends along said direction by portions which are inclined at angles of more than 7 with respect to said direction, the slopes of said first-named portion and of said second-named portions having like sign.

14. Apparatus as defined in claim 11 in which there is a differential pressure between the gas in said gas-supply means and the gas in said chamber and a diiferential pressure between the gas in said chamber and the gas in said gas-exl1aust means and in which said valve member is formed with a portion co-operating with said gas-supply means for gradually varying the conductance of said gas-supply means in response to movement of said valve member and a portion co-operating with said gas-exhaust means for gradually varying the conductance of said gas-exhaust means in response to movement of said valve member, the rates of variation of the conductances of said gas-supply means and said gas-exhaust means being respectively substantially inversely proportionate to the differential pressure between the gas in said gassupply means and the gas in said chamber and the differential pressure between the gas in said chamber and the gas in said gas-exhaust means.

15. Apparatus for damping pulses in a liquid comprising a flexible member having at least two sides and adapted to be mounted with one of said sides in contact with a liquid in which there are pulses to be damped,

a hollow, walled chamber connected to said flexible member, at least a portion of said flexible member forming at least a portion of a wall of said chamber, the second side of said member being exposed to the interior of said chamber,

gas-supply means for supplying a gas to the interior of said chamber,

diflerential-pressure-regulator means connected to said chamber and said gas-supply means for maintaining a desired diflerential pressure between the gas in said gas-supply means and the gas in said chamber,

gas-exhaust means connected to said chamber for exhausting said gas from the interior of said chamber,

valve means connected to said gas-supply means and said gas-exhaust means for controlling the conductances of said gas-supply means and said gas-exhaust means, and

valve actuating means operatively coupled with said flexible member and said valve means for controlling said valve means, whereby movement of said flexible member in response to a change in the instantaneous mean pressure of said liquid produces a corresponding change in the instantaneous mean pressure of said gas in said chamber for maintaining said flexible member in condition to vibrate in response to said pulses.

16. Apparatus as defined in claim 15 in which said diiferential-pressure-regulator means comprises valve means in said gas-supply means adapted in combination with said valve means connected to said gas-supply means and said gas-exhaust means to control the conductance of said gas-supply means and a flexible member connected to said valve means in said dilferential-pressure-regulator means for con- 13 14 trolling said valve means in said differential-pressure References Cited in the file of this patent regulator means, said flexible member connected to UNITED STATES PATENTS said valve means in said diflerential-pressure-regulator means being responsive to the pressure in id 1,862,228 Marsh June 7, 1932 chamber to control said valve means in said differen- 5 2,852,033 Orser Sept. 16, 1958 tial-pressure-regulator means. 2,993,472 Ladd July 25, 1961 UNITED" STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,,130351 April 28, 1964 Kasimir Lopas I It is hereby certified that war appears in. the above numbered patent requiring" correction and that the said Letters Patent shouldread as corrected be'lo' Column 8 line 32,, for "shown" read show line 67 for "or" first occurrence, read to column ll line 22 for "monnected" read connected same column 11 line 49 for "on" read one column 14 line 6 for 2 993 4I72" Signed and sealed this 18th day of August 19640 (SEAL) Attest:

ERNEST W. SWIDER' EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. APPARATUS FOR DAMPING PULSES IN A FLUID, COMPRISING A FLEXIBLE MEMBER HAVING AT LEAST TWO SIDES AND ADAPTED TO BE MOUNTED WITH ONE OF SAID SIDES IN CONTACT WITH A FIRST FLUID IN WHICH THERE ARE PULSES TO BE DAMPED, A HOLLOW, WALLED CHAMBER CONNECTED TO SAID FLEXIBLE MEMBER, AT LEAST A PORTION OF SAID FLEXIBLE MEMBER FORMING AT LEAST A PORTION OF A WALL OF SAID CHAMBER, THE SECOND SIDE OF SAID MEMBER BEING EXPOSED TO THE INTERIOR OF SAID CHAMBER, FLUID-SUPPLY MEANS CONNECTED TO SAID CHAMBER FOR SUPPLYING A SECOND FLUID TO THE INTERIOR OF SAID CHAMBER, FLUID-EXHAUST MEANS CONNECTED TO SAID CHAMBER FOR EXHAUSTING SAID SECOND FLUID FROM THE INTERIOR OF SAID CHAMBER, VALVE MEANS CONNECTED TO SAID FLUID-SUPPLY MEANS AND SAID FLUID-EXHAUST MEANS FOR CONTROLLING THE CONDUCTANCES OF SAID FLUID-SUPPLY MEANS AND SAID FLUIDEXHAUST MEANS, AND VALVE-ACTUATING MEANS OPERATIVELY COUPLED WITH SAID FLEXIBLE MEMBER AND SAID VALVE MEANS FOR CONTROLLING SAID VALVE MEANS, WHEREBY INCIPIENT MOVEMENT OF SAID FLEXIBLE MEMBER IN RESPONSE TO A CHANGE IN THE INSTANTANEOUS MEAN PRESSURE OF SAID FIRST FLUID IN THE VICINITY OF SAID FLEXIBLE MEMBER PRODUCES A CORRESPONDING CHANGE IN THE INSTANTANEOUS MEAN PRESSURE OF SAID SECOND FLUID IN SAID CHAMBER FOR MAINTAINING SAID FLEXIBLE MEMBER IN CONDITION TO VIBRATE IN RESPONSE TO SAID PULSES. 